Escape wheel



H. L. BEEHLER ESCAPE WHEEL Sept. 26, 1933.

Filed Dec. 27, 1929 gnw'ntoz Patented Sept. 26, 1933 ESCAPE WHEEL HowardL. Beehler, Lancaster, Pa., assignor to Hamilton Watch Company,Lancaster, Pa., a corporation of Pennsylvania Application December 27,1929 Serial N0. 416,953

Claims. (Cl. 58-116) As is well-known, a watch mechanism, or movement,containing parts of magnetic material, or which are sensitive tomagnetism, or a magnetic field to which the movement is exposed,

5 may have its accuracy impaired, or indeed under some conditions, itsrunning may be stopped.

Magnetic influences are especially hurtful in the case of the escapewheel, for in a strong magnetic field it may be stopped, or held fromrunning, and.even after removal from the magnetic field, the permanentmagnetism retained by the wheel may cause a variation in the rate of theWatch. Steel escape wheels are used in all high grade Watches and, ofcourse, it is of especial importance in high grade Watches to eliminateor prevent any disturbing factors in the running of the watch. Steel isdesirable because of its ability to withstand wear of the escape wheelteeth under the impact and friction of the pallet. The problem presentedtherefore is the provision of an escape wheel which will be free frommagnetic influences that would impair the accurate or proper running ofthe watch, and which will be able to withstand wear from the action ofthe pallet thereon. Brass is a non-magnetic material, but it is not hardenough to resist wear so that while its use for an escape wheel wouldeliminate the effect of magnetic influences, it would fail for want ofwear resisting properties. Of course important considerations to betaken into account in the solution of the problem are matters whichaffect manufacturing such as commercial feasibility from themanufacturers standpoint and the relation of an escape wheel constructedto eliminate or withstand magnetic influences and resist wear to otherparts or members of the movement, and which for example, involve thermalor temperature effects on the watch parts. An escape wheel might beproduced which would remove magnetism as a disturbing cause, and whichwould take care of the question of wear, but might be a failure from thecommercial and other considerations just mentioned. I have had all theseconsiderations in mind in producing my invention, and by my invention Ihave produced an escape wheel which meets all of the conditionsinvolved.

My invention consists of the escape wheel and a method of making thesame having the characteristics defined by or included within the termsor scope of he appended claims.

In what I now consider the best embodiment of my invention, and which Iwill use in exemplification of an embodiment of my invention, Iconstruct the escape wheel so that it has a main or body part ofwheel-form, that is to say, a hub, spokes and rim or circumference, of anon-magnetic material, such as brass, and teeth of steel.

I have found that by making the teeth or those portions (which I shallterm for convenience (10 tips) with which the pallet stones havecontact, of steel, that the quantity of the steel is so small as torender the effects of magnetism negligible. Besides the elimination ofmagnetism as a disturbing influence, an escape wheel so constructed hasor may have its change under thermal changes similar or substantiallysimilar to that of the metal plates in which the escapement is mounted,and thus avoid or prevent any change of depthing of the pallets in theescape wheel teeth. With the escape wheel and the movement platessupporting the escapement made of steel, and brass or German silver,respectively, the different coefficients of expansion of the different 7metals should result in change in depthing of the pallets on the teeth.Such an escape wheel may be easily and, therefore, cheaply manufactured.

A satisfactory method of manufacture is the production of a compositedisc-form blank of brass and steel brazed together which by subjectionto certain operations is converted into an escape wheel having body andteeth tips with the characteristics above set forth.

In the drawing:

Fig. 1 is a plan View of an escape wheel made in accordance with myinvention, shown in operative relation to the pallet;

Fig. 2 is an edge view thereof;

Figs. 3 and 4 are, respectively, a top plan view and a cross section ofthe steel member used in forming the blank from which the final Wheel ismade;

Figs. 5 and 6 are similar views showing the assembled brass and steelmembers previous to brazing;

Figs. '7 and 8 are view similar to Figs. 5 and 6 showing the stage afterbrazing;

Fig. 9 is a cross section showing the composite blank after the removalof the surplus brass following the brazing operation;

Fig. 10 is a cross section of the disc-form blank reduced to thethickness of the finished escape wheel and consisting of a central discof brass and a rim of steel;

Fig. 11 is a top plan view of the blank as prises the main or body wheelpart which consists of a hub, 10, spokes, 11, a circumference or rim,12, all of brass, and teeth portions or tips, 13, of steel. The teeth,13, as I have already explained, are joined to the wheel body bybrazing, so that they are as much a part of the wheel as ifhomogeneously integral therewith. The pallet, 14, is of customaryconstruction and includes teethengaging jewels, 15.

Describing now by reference to Figs. 3 to 11, a method for producing myescape wheel, I provide a disc, 16, of steel with a central circularcavity, 17, in one side in which I place a solid disc, 18, of brass of adiameter corresponding to the external diameter of the finished wheelrim, 12. The brass disc, 18, is thicker than the depth of the circularrecess, 1'7, in the steel cup so that as shown in Fig. 6, it projectsslightly above the adjacent surface of the cup. A suitable brazing fluxis applied to the brass and steel assembled members and by means of afurnace which subjects the brass to a melting temperature, the brass andsteel are brazed together in a solid, permanent union, the product ofthis treatment being illustrated in Figs. 7 and 8. The excess brassappearing in Figs. '7 and 8 is then removed by a facing operation and ifdesired, to enable hardness measurement to be made. The next step is toface the composite blank on the reverse side to remove the bottom of thesteel cup and to produce the blank shown in Fig. 10 which consists ofthe central disc, 19, of brass and the annular rim, 20, of the properthickness for the finished wheel. In this stage, or previously, ifdesired, the steel can be hardened and drawn to the proper temperaturerequired for the final or finished escape Wheel teeth. Next, as shown inFig. 11, by punching the disc shown in Fig. 10, the hub or center,spokes and rim of the brass disc, 19, are formed and to give theexternal diameter to the steel rim, 20, proper for the teeth. The blankin the stage shown in Fig. 11, can be placed in the standard machinesfor cutting escape wheels and the teeth cut and polished in the standardor usual manner, so that the final operations require no new or unusualmachines, but may be performed by the standard or cus tomary machines.

Should it be desirable to temper the material from which the body partof the escape wheel is made, this can be done by hammering or swagingthe spokes, center and rim after the punching operation and the productof that treatment then shaved to the proper size.

It is possible in producing an escape wheel in accordance with myinvention to have teeth of such hardness or Wear resisting properties asto enable steel pallet stones to be used instead of jewels.

What I claim is:

1. An escape wheel having a main or body portion of non-magneticmaterial and teeth of different, harder and wear-resisting material.

2. An escape wheel having a main or body portion of non-magneticmaterial and teeth of different, harder and wear-resisting material, thebody and teeth being brazed together.

3. An escape wheel having a main or body portion of non-magneticmaterial and teeth portions of different, harder and wear-resistingmaterial, the teeth being of steel.

4. An escape wheel having a main or bodv portion of non-magneticmaterial and teeth portions of different, harder and wear-resistingmaterial, the body being of brass and the teeth of steel.

5. An escape wheel having a main or body portion of non-magneticmaterial and teeth of diiierent, harder and wear-resisting materialassociated with movement plates, the body portion having a coefficientof expansion the same or substantially the same as the movement plates.

HOWARD L. BEEHLER.

